Stable fuel oil compositions



Patented May 11, 1954 UNITED STATS NT OFFICE STABLE FUEL OILCOMPOSITIONS poration of Delaware No Drawing. Application March 28,1950, Serial No. 152,496

6 Claims.

This invention relates to stable fuel oil compositions. Moreparticularly, the invention relates to stable fuel oil compositionswhich are composed of straight run and catalytically cracked oils.

When a heavy petroleum oil is subjected to catalytic cracking by any ofthe conventional processes such as the fixed bed, moving bed or fluidprocesses, wherein the heavy oil is contacted with a cracking catalystsuch as a natural clay catalyst or a synthetic silica-alumina orsilica-magnesia catalyst, the conversion products comprise not onlygasoline hydrocarbons but also heavier distillate hydrocarbons, such ashydrocarbons boiling in the fuel oil range; that is, hydrocarbonsboiling within the range of about 350 to about 750 F. Although theburning characteristics of such oils are fairly good, it is generallythe practice when using these catalytically cracked oils as fuels to mixthem with straight run distillate oils of similar boiling range in orderto produce mixed oils having better burning characteristics than thecatalytically cracked oils, and also in order to balance refineryproduction.

These mixed straight run and catalytically cracked distillate oils,however, have been found to have the disadvantage of being relativelyunstable in storage. After a few months in storage at atmospherictemperature, they tend to form a precipitate or sludge which isunsightly and which reduces their usefulness as burning oils in certaintypes of installations. It has been found that the storagecharacteristics of a mixed oil are poorer than the characteristics ofeither oil alone. The reason for this is not clearly understood but itmay be that the solubility of certain degradation products of thecatalytically cracked oil is less in the mixed oil than in thecatalytically cracked oil.

The present invention relates to fuel oil compositions comprising mixedcatalytically cracked and straight run distillate fuel oils whichcompositions are of improved stability with respect to sludge depositionand therefore of good appearance and adapted for effective use in fueloil furnaces and as diesel fuels even after being stored for extendedperiods. We have discovered that such an improved mixed fuel oil can beobtained by incorporating in the oil a small amount of a combination ofa trialkylphosphite in which the alkyl groups are open or cyclic alkylgroups containing 4 to 12 carbon atoms and a salt of a metal of group IIof the periodic table and a dialkyl dithiophosphoric acid in which thefit alkyl groups are also open or cyclic and contain l to 12 carbonatoms. The barium, calcium, magnesium and zinc salts of such dialkyldithiophosphoric acids are especially important. A preferred combinationcomprises the barium salts of mixed dialkyl dithiophosphoric acids inwhich the alkyl groups are open chain and contain an average of 6 to 8carbon atoms, in combination with tributylphosphite. As will appear fromthe specific examples, we have found that while a compound of either ofthese classes is relatively ineffective when incorporated in a mix-edfuel oil, the combination is effective in inhibiting sludge formation.The two compounds may be employed in varying proportions with respect toone another, provided the compound present in the smaller amount ispresent in an amount corresponding to at least about 0.005 per cent byweight of the finished oil. In general it is preferred to employ thecompounds in weight ratios varying from about 1:4 to 4:1.

It has not been determined in what way combinations of compounds ofthese classes function to improve thecharacteristics of the mixed fueloil and therefore the invention is not limited to any theory ofoperation. It might appear that they function as solubilizing agents forthe sludge, but this function is more or less negatived by the fact thatwhereas a mixed fuel oil in the absence of such a combination formsadditional amounts of sludge so long as it is stored, at least over anyfeasible test storage period, the incorporation of a combination of thisclass in the oil inhibits the formation of sludge even after some sludgehas been formed, and the already formed sludge does not disappear. 'Byadding a small amount of combination of compounds as described to amixed fuel oil containing an amount of sludge making the oil undesirablefor use in many burner installations because of sludge deposits, the oilcan be employed in such installations without leaving undesirabledeposits. In this case it appears that although the sludge does notdisappear, its characteristics are so changed as to prevent itsdeposition on a typical burner screen or on other parts of a burner.

The addition of the combination in very small amounts has been found toproduce the best results. Thus, fully effective results are obtainedwhen using between about 0.05 and about 0.15 per cent of the combinationby weight of the mixed fuel oil even when the mixed oils have highsulfur content and pronounced sludging tendencies. However, adequateresults are obtained when using as little as 0.01 per cent of thecombination. In this case, in many instances full inhibition of sludgeformation is not obtained but the mixed oil is satisfactory for usebecause the combination changes the physical, and perhaps chemical,nature of the sludge so that it does not cause rapid clogging of screensand other parts of burners. While larger quantities than 0.15 per centcan be used, no advantage appears to result. The use of largerquantities necessarily increases the ash and carbon residue test valuesof the mixed oils, and sometimes also causes darkening.

The compounds may be incorporated in the mixed fuel oil in any suitablemanner. For example, they may be added either separately or together toeither or both of the catalytically cracked or straight run oils priorto mixing the two or they may be added to the mixed oil. When thecompounds are incorporated in the mixed oil, it is unnecessary to dothis immediately after mixing the oil as they are effective even aftersome sludge has formed. It will usually be preferable to add thecompounds prior to any sludge formation as this will either eliminatesludge formation, or reduce the amount of sludge formed, depending uponthe specific characteristics of the oils employed in making up the mixedoil. The compounds can be added as such but it is preferred to employthem in the form of concentrated solutions in an oil carrier. Afteraddition, some circulation of the mixed oil is desirable to insure theearly production of a uniform composition, but this is not absolutelynecessary.

The problem with which the present invention is concerned exists onlywhen a catalytically cracked oil and a straight run oil are combined insuch proportions as to cause a substantial effect such as previouslydescribed. The invention is important when the ratio of the volume ofthe catalytically cracked oil to the straight run oil is within therange of 9:1 to 1:9. It is especially advantageous when applied to mixedoils containing these oils in a volume ratio within the range of 4:1 to1:4.

In order to determine the efiectiveness in mixed fuel oils of compoundsof the classes disclosed above, two tests were carried out, a lightstability test and a storage test. The light stability test was carriedout by exposing a 100 cc. sample of the oil to be tested to a lightsource rich in ultra-violet rays, for periods of i hours alternated withperiods of 20 hours during which the oil was stored in the dark. Thetest was completed after 40 hours exposure to the light. At the end ofeach dark storage period the samples were examined for the presence ofprecipitated sediment or sludge. The exposure to light was accomplishedby putting samples of fuel oil in i-ounce bottles which were unstopperedto allow access of air. These bottles were placed within a circularmetal enclosure at a distance of 22 inches from the light source whichwas a Westinghouse 400 watt type DI-I-l mercury vapor lamp mountedvertically in the center of the housing. It was found that a temperaturerise of 20 F. occurs during the exposure period. The interval ofdarkness was necessary to allow any dispersed sludge to settle and topermit oxygen to replace any used up in the light-induced reaction. Theeffect of the exposure to light was judged by swirling the bottle andestimating the quantity of precipitate which had settled. This wasrecorded as Trace, Light, Medium or Heavy.

The storage test was carried out by pouring 1500 cubic centimeters ofthe fuel to be tested into a two-quart Mason jar and immersing an 8 inchby 1 inch by inch SAE 1020 cold rolled steel strip in the oil. The steelsurface to oil ratio approximates that existing in a 55 gallon steeldrum. The jar was then closed with a vented lid and was stored in totaldarkness. Periodically sampling and testing were carried out as rapidlyas possible in subdued light. The extent of deterioration of the fuelwas determined by the amount of precipitate observed and designated asTrace, Light, Medium or Heavy. Any staining or corrosion of the steelstrip was noted.

In the following tables there are given the results of light stabilityand storages tests made on mixed fuel oils of the character indicated inthe absence of an additive and containing a compound or compounds of theclasses disclosed above. The compounds employed in these tests were thebarium salt of a mixture of dialkyl dithiophosphoric acids, in which thealkyl groups were open chain and contained an average of about '7 carbonatoms, which is designated in the following tables as Compound I, andtributylphosphite. Compound I was employed in the form of a 50 per centsolution in a hydrocarbon oil, but the percentages of this compound usedin the tests are based on the weight of the compound itself.

The ratios of the oils employed are volume ratios and the percentages ofthe added compounds are percentages of the weight of the mixed oil. Theterm No. 2 indicates an oil boiling within the range of about 350 to 750F. and having a minimum API gravity of 26.

The following Table I presents the data obtained in light stabilitytests.

Table 1 Light Stability Test No. of Hours Exposure to Ultra-Violet LightRe- Mixed Oi] quired to Sludge Oil Amount to of Sludge at End of TestTrace Light fg Heavy 1. 50/50 Blend Eastern Vene 0 12 28 40 Heavy.

zuela Straight Run No. 2 Fuel Oil and Fluid Catalytically Cracked No. 2Disillate, N o Additive. 2. Blend No. 1 plus 0.05% 4 20 40 Medium.

Compound I. 3. Blend No. 1 plus 0.025% 4 12 28 Do.

Compound I. 4. Blend No. 1 plus 0.1% Tri- 4 8 20 24 Heavy.

butylphosphite. 5. Blend No. 1 plus 0.05% 4 8 20 28 Do.

Tributylphosphite. 6. Blend No. 1 plus 0.025% 4 24 Light.

Oom ound No. 1 and 0.05 o Tributylphosphite.

Table. II

Mixed Oil Storage Test-Precipitate Formed and Condition of Metal Strip 1Month 3 Months 6 Months .50/50 Blend Eastern Venezuela Straight; Run No.2 Fuel Oil and Fluid Catalytically Cracked No. 2 Distillate, No-Additive.

. Blend No. 1 plus 0.025% Compound I and 0.05% Tributylphosphlte. .80/20Blend Eastern Venezuela Straight Run No. 2 Fuel Oil and FluidCatalytically- Cracked No. 2 Distillate, No-Additive.

. Blend No. 3 plus. 0.025% Compound I and 0.05% Tributylphosphite.

. 50/50 Blend West Texas Straight Trace K Light, 0 K

Medium, OK

Medium, Sl. Stain Light, 0 K

Medium, OK

Light, OK.

Medium, 0 K

Heavy, Stained.

Light, OK.

Medium+ Stained.

Light", OK.

Heavy, Rust.

Run No. 2 Fuel Oil and Thermofor Gatalytically Cracked No. 2 Distillate,No Additive.

6. Blend N0. 5 plus 0.05% Cornpound I and 0.1% Trioutylphosphite.

7. Blend N0, 5 plus 0.025% Cempound I and 0.05% Tributylphosphite.

8. 80/20 Blend West Texas Straight Run No. 2 Fuel Oil and ThermoforCatalytically Cracked No. 2 Distillate, No Additive.

0. Blend No. 8 plus 0.05% Oompound I and 0.1% Tributylphosphite.

. Blend No. 8 plus 0.025% Compound I and 0.05% 'lributylphosphite.

Trace+, OK

Trace, OK

I Medium, Stained...

Trace, OK

Trace+, OK

Trace, OK

Heavy, Stained T1ace+,.OK

Trace+, S1. Rust Light+, 01;.

Light, ox.

Heavy, Stained.

Light, S1. Rust.

*Five months only.

From Table II it will be seen that various mixtures of straight run.and, catalytically cracked distillate fuel Oils. are materially improvedwith respect to stability in storage by the addition of mixtures ofCompound I and tributylphosphite.

Although the compounds employed in the tests, the results of which aregiven in the tables, are preferred for use in the fuel oil compositionsof the invention, it will be understood that other members of theclasses of compounds disclosed above may be used to prepare fuel oilcompositions of substantially the same improved properties. Examples ofother suitable dialkyl dithiophosphoric acid compounds are the barium,calcium, magnesium and zinc salts of such acids wherein the alkyl groupsare hexyl, cyclohexyl, octyl, decyl, dodecyl or mixtures of these groupsand isomers such as 2-ethylhexyl, ZAA-trimethylpentyl,2,446,6-pentamethylheptyl.

In place of tributylphosphite there may be used triamylphosphite,trioctylphosphite, monobutyldioctylphosphite, etc. The tributylphosphitemay be the normal butyl, isobutyl, or tertiary butyl compound.

The tests employed in obtaining the data set out above are especiallysevere tests of the compounded oils and the results are given in termsof the quantity of sludge deposited without regard to the nature of thesludge. In practice, however, the quantity of sludge formed isfrequently not as important as the physical characteristics of thesludge. The addition of a very small amount of a combination of acompound of the classes described to a mixed fuel oil affects thecharacteristics of the sludge, making it lighter and apparently moreeasily dispersed so that sludge deposition in use is avoided or at leastmaterially lessened. To accomplish variation in the nature of the sludgeas well as some control over the actual formation of sludge as little as0.005 per cent by weight of the mixed oils of each component of thecombination, or a total of 0.01 per cent of the combination can be used.Thus, we generally prefer to employ each component in an amount equal toabout 0,005 to about 0.05 per cent by weight of the mixed oils. Inxanycase, no more than about 0.25 per cent of the combination should be usedsince with larger amounts undesirable color changes frequently occur.

If desired, the stable fuel oil compositions may contain in addition tothe compounds previously discussed oxidation inhibitors, corrosioninhibitors, antifoam agents, flash point control agents, ignitionquality improvers, or combustion improvers and other additives adaptedto improve the oils in one or more respects.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may be made without departing from the spirit orscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1. A fuel oil composition comprising a major proportion of a mixture ofstraight run and catalytically cracked distillate fuel oils tending todeposit sludge and containing a small amount of a combination of a saltof a metal of group II and a dialkyl dithioposphoric acid in which thethe alkyl groups contain 4 to 12 carbon atoms, and of atrialkylphosphite in which the alkyl groups contain 4 to 12 carbonatoms, said small amount being sufficient to inhibit sludge depositionfrom said mixture of oils and comprising at least 0.005% by weight ofsaid mixture of oils of each of said salt of said dialkyldithiophosphoric acid and of said trialkylphosphite and not more than0.25% of said combination by weight of said mixture of oils.

2. A fuel oil composition comprising a major proportion of a. mixture ofstraight run and catalytically cracked distillate fuel oils tending todeposit sludge and containing a small amount of a combination of thebarium salt of mixed dialkyl dithiophosphoric acids in which the alkylgroups are open chain and contain an average of about 7 carbon atoms,and of a trialkylphosphite in which the alkyl groups contain 4 to 12 7.carbon atoms, said small amount being sufficient to inhibit sludgedeposition from said mixture of oils and comprising at least 0.005% byweight of said mixture of oils of each of said salt of said dialkyldithiophosphoric acid and of said trialkylphosphite and not more than0.25% of said combination by weight of said mixture of oils.

3. A fuel oil composition comprising a major proportion of a mixture ofstraight run and catalytically cracked distillate fuel oils tending todeposit sludge and containing a small amount of a combination of a saltof a metal selected from the group consisting of barium, calcium,magnesium and zinc, and a dialkyl dithiophosphoric acid in which thealkyl groups contain 4 to 12 carbon atoms, and if tributylphosphite,said small amount being suflicient to inhibit sludge deposition fromsaid mixture of oils and com prising at least 0.005% by weight of saidmixture of oils of each of said salt of said dialkyl dithiophosphoricacid and of said tributylphosphite and not more than 0.25% of saidcombination by weight of said mixture of oils.

4. A fuel oil composition comprising a major proportion of a mixture ofstraight run and catalytically cracked distillate fuel oils tending todeposit sludge and containing a small amount of a combination of thebarium salt of mixed dialkyl dithiophosphoric acids in which the alkylgroups are open chain and contain an average of about 7 carbon atoms,and of tributylphosphite, said small amount being sumcient to inhibitsludge deposition from said mixture of oils and comprising at least0.005% by weight of said mixture of oils of each of said salt of saiddialkyl dithiophosphoric acid and of said tributyphos- 8. phite and notmore than 0.25% of said combination by weight of said mixture of oils.

5. A fuel oil composition comprising a major proportion of a mixture ofstraight run and catalytically cracked distillate fuel oils tending todeposite sludge and containing a small amount of a combination of a saltof a metal selected from the group consisting of barium, calcium,magnesium and zinc, and a dialkyl dithiophosphoric acid in which thealkyl groups contain 4 to 12 carbon atoms, and of a trialkylphosphite inwhich the alkyl groups contain 4 to 12 carbon atoms, said small amountbeing sufiicient to inhibit sludge deposition from said mixture of oils,and comprising from about 0.005 to about 0.05 per cent by weight of saidmixture of oils of each of said salt of said dialkyl dithiophosphoricacid and of said trialkylphosphite.

6. A fuel oil composition as defined in claim 5 in which said salt ofsaid dialkyl dithiophosphoric acid is the barium salt of mixed dialkyldithiophosphoric acids in which the alkyl groups are open chain andcontain an average of about 7 carbon atoms, and said trialkylphosphiteis tributylphosphite.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,252,985 Rutherford et al. Aug. 19, 1941 2,261,227 Cloud NOV.4, 1941 2,405,560 Campbell Aug. 13, 1946 2,527,987 Caron et al. Oct. 31,1950 2,552,570 McNab et a1 May 15, 1951

1. A FUEL OIL COMPOSITION COMPRISING A MAJOR PROPORTION OF A MIXTURE OFSTRAIGHT RUN AND CATALYTICALLY CRACKED DISTILLATE FUEL OILS TENDING TODEPOSIT SLUDGE AND CONTAINING A SMALL AMOUNT OF A COMBINATION OF A SALTOF A METAL OF GROUP II AND A DIALKYL DITHIOPOSPHORIC ACID IN WHICH THETHE ALKYL GROUPS CONTAIN 4 TO 12 CARBON ATOMS, AND OF ATRIALKYLPHOSPHITE IN WHICH THE ALKYL GROUPS CONTAIN 4 TO 12 CARBONATOMS, SAID SMALL AMOUNT BEING SUFFICIENT TO INHIBIT SLUDGE DEPOSITIONFROM SAID MIXTURE OF OILS AND COMPRISING AT LEAST 0.005% BY WEIGHT OFSAID MIXTURE OF OILS OF EACH OF SAID SALT OF SAID DIALKYLDITHIOPHOSPHORIC ACID AND OF SAID TRIALKYLPHOSPHITE AND NOT MORE THAN0.25% OF SAID COMBINATION BY WEIGHT OF SAID MIXTURE OF OILS.